Qi GU

Human tissues are big complicated physiological system but with basic cell unit at microscale, which thus in turn requires biofabrication strategies such as bioprinting with not only the enormous control over high deposition resolution and complex geometries of blood vessels, but also supply environment to regulate intrinsic cell signaling. Current approaches have had limited success at multi-scale vascular connection due to the incoordination between cell-laden materials and stability of perfusion channel. Developing new bioactive materials to rationally augment cell viability is still an enormous challenge, owing to the nutritionally deficient environment caused by the limited-penetration distance of nutrition when cells are encapsulated within biomaterials.

Here, we report a methodology to fabricate soft vascularized liver-like tissue at centimeter-scale with high viability and accuracy using multi-materials bioprinting involving inks with low viscosity and a customized multistage-temperature-control printer. The printed constructs could be perfused with branched vasculature with well-formed 3D capillary network and lumen, which would potentially supply the cellular components with sufficient nutrients in the matrix and to mimic a mature and functional liver tissue with increased functionality in terms of synthesis of liver specific proteins and subperitoneal grafting. Moreover, an elastic layer (5% gelatin methacryloyl) was printed wrapping sacrificial ink to support the direct surgical anastomosis of the carotid artery to the jugular vein. Additionally, based on the up-mentioned system, we show a strategy to 3D print skeletal muscle followed by sequential culture processes. We observed the confined area effects on skeletal muscle maturation in terms of the aligned arrangement, specific gene expression and even mechanical forces. Our findings demonstrated the dynamic changes of skeletal muscle tissue during in vitro 3D construction and reveal the role of physical factors in the orientation and maturity of muscle fibers.

For the materials, we have developed a serious of bioinks such as a cationic conjugated polythiophene derivative, poly[3-(3’-N,N,N-triethylamino-1’-propyloxy)-4-methyl-2,5-thiophene hydrochloride] (PMNT) is designed and integrated into anionic gelatin/alginate matrix to develop a new 3D bioprintable conjugated polymer ink Gel/Alg/PMNT, while the electrostatic interaction can assist PMNT to anchor inside ink without severe diffusional loss. he inherent highly bioactive and robust proliferation-promoted nature of the developed conjugated polymer ink Gel/Alg/PMNT significantly overcome the nutritionally deficient environment especially in 3D printed large scale architectures.

In sum, we have made some advances in combining 3D bioprinting, biomaterials, printing stem cells to fabricate functional tissues, delivering insights into the fundamentals of stem cell dynamics in 3D and understanding the mechanism of stem cell fate regulation and cell migration in 3D environments.